title: Occupational risk factors for osteoarthritis of the knee: a meta-analysis.
abstract: BACKGROUND
  Systematic reviews agree that knee osteoarthritis (OA) is related to occupational activities, but have not quantified the overall risks.
  
  
  METHODS
  Systematic review of observational studies of knee OA and occupation. Job titles, elite sport, heavy work, kneeling, and other activities were included. Relative risk estimate and 95% confidence interval (CI) compared to sedentary work were retrieved or calculated for meta-analysis. Publication bias was examined with Egger tests and heterogeneity was determined with I(2) values and Q tests. Subgroup analysis was performed to examine causes of heterogeneity. A random effects model was performed to combine the data.
  
  
  RESULTS
  Studies of knee OA (n=51), persistent knee pain (n=12) and knee OA progression (n=3) were retrieved. Occupational risks for knee OA were examined in a total of 526,343 subjects in 8 cohort/prospective/longitudinal studies, 25 cross-sectional studies and 18 case control studies. The overall odds ratio (OR) was 1.61 (95% CI 1.45-1.78) with significant heterogeneity (I(2)=83.6%). Study designs showed a positive association between knee OA and occupational activities; cohort (OR 1.38, 95% CI 1.10-1.74), cross-sectional (OR 1.57, 95% CI 1.37-1.81) and case control (OR 1.80, 95% CI 1.48-2.19). Overall there was evidence of publication bias (P<0.0001) which was apparent in the cross-sectional and case control studies (P<0.0001 and P=0.0247 respectively).
  
  
  CONCLUSIONS
  Some occupational activities increase the risk of knee OA, although the influences of publication bias and heterogeneity are important limitations of this study. Prospective studies would greatly improve the evidence base.
authors.affiliation: Academic Rheumatology, University of Nottingham, UK. dan.mcwilliams@nottingham.ac.uk
authors.forename: D F
authors.initials: DF
authors.lastname: McWilliams
authors.forename: B F
authors.initials: BF
authors.lastname: Leeb
authors.forename: S G
authors.initials: SG
authors.lastname: Muthuri
authors.forename: M
authors.initials: M
authors.lastname: Doherty
authors.forename: W
authors.initials: W
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000209:etiology*; D016273:Occupational Exposure / Q000009:adverse effects*; D016017:Odds Ratio; D020370:Osteoarthritis, Knee / Q000209:etiology*; D012307:Risk Factors